Variable stroke press



July 28, 1959 w. F. LONGFIELD 2,896,457

VARIABLE STROKE PRESS Filed July 1a, 1956 I 4 Sheets-Sheet 1 IN V EN TOR.

WILLIAM E LONGFIELD ATTORNEY y 1959 I w. F. LONGFIELD 2,896,457

' VARIABLE STROKE PRESS Filed July is, 1956 4 Sheets- Sheet 2 IN V EN TOR.

WILLIAM E LONGF'IELD ATTORNEY y 1 1959 w. F. LONGFIELb 2, 57

4 VARIABLE STROKE PRESS Filed July 18, 1936' 4 sheets-sheet s IN V EN TOR.

WILLIAM FI LONGFIELD y 1959 w. F. LONGFIELD 2,396,457

VARIABLE STROKE PRESS Filed July 18, 1956 4 Sheets-Sheet 4 INVENTOR.

WILLIAM F. LONG FIELD Arnauzy United States Patent M VARIABLE STROKE PRESS William F. Longfield, Warren, Ohio, assignor to The Federal Machine & Welder Company Application July 18, 1956, Serial No. 598,695

'5 Claims. (Cl. 74-43) the movable platen depends, to a large degree, upon the linear speed attained by such platen. Many factors may limit the aforementioned linear speed; for example, it may be limited by the design of the press itself, by the nature of the material being worked, or by the die parts or other material working devices carried by the respective press platens.

, Since the linear speed of the movable press platen is directly proportional to the distance it travels during its stroke, it will be clear (assuming a constant linear speed) that a short stroke press will be capable of delivering a greater number of strokes per minute than will one of a larger stroke. Unfortunately, many operations require presses having relatively long strokes while for others, a shorter stroke is adequate. In order to provide presses capable of eflicient use in various types of operations, it has heretofore been proposed to so construct such presses that their strokes may be adjusted.

The present invention provides an adjustable stroke press. This, in itself is not new; however, the invention represents a great advance over presses of this type heretofore known in that the stroke adjustment is accomplished by a simple, relatively inexpensive construction. Further, the press stroke may be easily and quickly changed with a minimum of adjustments so as to minimize down time of the press. These and other advantages will readily become apparent from a study of the following description and from the drawings appended hereto.

In the drawings accompanying this specification and forming a part of this application there is shown, for purpose of illustration, an embodiment which the invention may assume, and in these drawings:

Figure 1 is a broken sectional view showing representative parts of a press embodying my invention, with operating mechanism shown in one position,

Figure 2 is a perspective view of certain elements of the press,

Figure 3 is an enlarged, fragmentary sectional view generally corresponding to the line 3-3 of Figure 2,

Figure 4 is a further enlarged fragmentary sectional view generally corresponding to the line 4-4 of Figure 3,

Figure 5 is an exploded perspective view of the parts shown in Figure 3,

Figure 6 is a view similar to Figure 3 but showing the position of the parts at a different portion of the press cycle,

Figure 7 is a view similar to Figure 6 but showing the parts positioned for a shorter stroke, and

2,896,457. Patented July 28, 1959 Figure 8 is a view similar to Figure 3 but showing the parts positioned for the shorter stroke.

The particular press selected to illustrate the present invention is known as a welding press and is of the type employed by the automobile industry for the high speed fabrication of automobile components. As seen in Figure 1, this press comprises a frame 110, a stationary upper platen 11, and a movable lower platen 12 which is reciprocable toward and away from stationary platen 11 along guide rods 13, 13. It is to be clearly understood, however, that the invention hereinafter to be disclosed may be applied with equal facility to suitable presses of other types which are adapted to be used for widely differing purposes.

In the fabrication of automobile components such as, for example, doors or the like, suitable metal stampings are usually clamped tightly together in proper assembled relation within a suitable welding jig or fixture and then permanently secured together by means of a suitable welding operation. In the present embodiment, such welding fixture is represented as being provided by an upper fixture portion 14 carried by fixed platen 11 and a lower fixture portion 15 carried by movable platen 12.

Either one, or both, of the fixture portions 14, 15 may carry welding guns, welding transformers and/or other pertinent fabricating equipment, depending upon the requirements of the work to be fabricated. Likewise, the parts to be fabricated may be loaded in either, or both, of the fixture portions 14, 15 depending upon the design of the fixture and the work to be fabricated therein.

Because the lower platen 12 moves vertically and in its lower position is more accessible to the operator, it may be preferable to design the fixture so that the parts to be assembled are loaded in lower fixture portion 15 and carried by upward movement of platen 12, to operable relation with upper fixture portion 14. As the fixture portions 14, 15 close on each other, the parts to be assembled are firmly held in located relation and at the proper time the welding guns are fired to weld the work parts together.

In normal operation, the parts to be assembled are loaded in the lower fixture portion 15 and lower platen 12 is then caused to move upwardly to a position adjacent the upper platen whereupon the work pieces will be welded together by welding guns carried by one or both of the fixture portions. Platen 12 will then be lowered to permit removal of the fabricated work parts and subsequent loading of additional unassembled work parts prior to the next press cycle.

With reference to Figures 1 and 2, lower platen 12 is adapted to be reciprocated along guide rods 13, 13 toward and away from upper platen 11 by means of the following: Links 16 have their lower ends 17 pivotally secured to lower platen 12 at. 18 and in the present embodiment, four links 16 are employed, one adjacent eachcorner of the platen. It will be apparent, however, thata greater or lesser number of links could be employed as circumstances require. Each link 16 has an olfset upper end 19 which is adapted to be pivotally connected, by means of respective crank pins 20, to respective crank arms 21 which are carried in paired, spaced-apart relation on respective spaced-apart shafts 22 suitably journaled to the press frame 10. Each crank pin 20 is carried by its respective crank arm in offset relation relative to the axis of its respective shaft 22 so that each crank pin moves in an arc about the axis of its shaft as the latter is rotated. p

In the position of parts shown in Figures 1 and 2, crank arms 21 extend downwardly from respective shafts 22 and lower platen 12 is in its lowermost position. When it is desired to raise the platen, shafts 22 will be rotated approximately degreesin the directions indicated sothat of illustration, the mechanism herein shown is similar to that disclosed in the application for Letters Patent filed by me on February 13, 1956, bearing Serial Number 565,084, and entitled, Press.

Briefly, the mechanism herein disclosed for effecting movement of shafts 22 comprises a relatively large gear 23 journaled on the press frame and driven in any suitable manner from a power source. Gear 23 rotates a crank 24 to which one end of a connecting rod 25 is journaled. A pair of toggle links 26 are pivotally connected to the other end of the connecting rod and each is in turn pivotally connected to respective bell crank levers 27 each pivotally supported by respective shafts 28. Connecting arms 29 are, pivotally connected to respective bell crank levers 27 and to respective gear sectors 30 which are pivotable about respective shafts 30a. Each gear sector 30 is in mesh with a gear 31 carried by respective spacedapart shafts 22.

In the position of parts shown in Figure 1, connecting rod 25 is at the top of its stroke so that, as before mentioned, crank arms 21 extend downwardly from respective shafts 22 and lower platen 12 is in its lowermost position. As gear 23 is rotated, connecting rod 25 will be moved to its lowermost position and by means of the linkage aforesaid, gear sectors 30 will efiect rotation of shafts 22 so as to cause crank arms 21 to extend upwardly to thereby elevate the lower platen and close the press.

The present invention has as a principal object the provision for easily and quickly adjusting the stroke of a press by means of a simple, low-cost construction. In the present embodiment, and by way of illustration only,

the press provides for a long stroke of 18 inches and a short strokeof 12 inches. Assuming a certain maximum permissible linear speed of the movable platen, the maximum permissible number of strokes per minute at the long stroke is 26 while at the short stroke, the maximum permissible number of strokes per minute is raised to 39 with no change in the linear speed of the movable platen.

In the position of parts shown inFigure l, the press is seen in its wide open position at its longest stroke setting. In thisposition, fixture portions 14, 15 are spaced-apart a distance indicated at A. However, the maximum spacing between fixture portions 14, 15 may be reduced, as indicated at B, in the event the wider spacing is not required for loading or unloading the work pieces between the fixture portions. As will later appear, the shorter stroke ofthe press permits operation at a speed to provide a greater number of strokes per minute without affecting the linear speed of the movable platen and, to accomplish the foregoing stroke adjustment, the following construction is presently provided.

As best seen in Figure 5, each crank arm 21 is preferably formed to provide spaced ears 32, 33 for receiving therebetween the upper portion 19 of respective links 16. Each crank arm 21 has provision for supporting crank pin 20 various distances from the axis of shaft 22 and, at the present time, each crank arm is provided with two pairs of apertures 34 and 35 for selectively receiving the crank pin. Each pair of apertures 34, 35 comprises two apertures in alignment with each other, oneof each pair being formed in ear 32 and the other formed in ear 33. It will be evident from the drawing that the pairs of apertures are not only spaced from each other but are also spaced different distances from the axis of shaft 22.

Upper end 19 of'each link 16, or more accurately, the bushings carried by the link provide a pair of apertures 36, 37 for closely receiving crank pin 20. The spacing between apertures 36, 37 is identical with the spacing be tween pairs of apertures 34,35 of the crank arm and as will become clear, aperture 36 is adapted to cooperate with the pair of apertures 34 while aperture 37 is adapted to cooperate with the pair of apertures 35.

When it is desired to change the stroke of the press and assuming the latter is set up for its longest stroke, that is, with respective crank pins 20 positioned in the pair of apertures 34 of respective crank arms 21 and in respective apertures 36 of respective links 16, the press will be operated to elevate movable platen 12 to its uppermost terminal position to thereby close the press. All of the crank arms 21 will thereupon be in the position shown in Figure 6. One crank pin 20 will then be removed from its crank arm 21, link 16 shifted slightly to align its aperture 37 with the pair of apertures 35 of the crank arm, and the crank pin then passed through the aligned apertures.

It is preferable that each of the crank pins 20 be re positioned in turn. In this way, the weight of the movable platen will always be supported by three links during repositioning of each crank pin. This obviates the necessity of juggling the movable platen up or down, by the use of jacks or the like as required by many prior art presses of the adjustable stroke type, in order to position the crank pin in its alternate position.

It will be understood that in setting up mechanical presses, it is usually a time consuming operation to adjust the press so that the fixture, or die, portions carried by respective press platens will meet properly when the press is in its closed position. In the event the fixture portions do not come together close enough when the press is closed, the material being operated upon will not be properly worked. In the event the fixture portions come too close together, interference therebetween may result which may damage the fixture portions and/or'the press itself. This adjustment is frequently made by properly positioning and then locking the fixed platen of the press in its adjusted position.

With many prior art, adjustable stroke presses, a change in stroke setting affects the position of the movable platen in the closed position of the press. That is, in a press of the present type having a fixed upper platen and a movable lower platen, changing the stroke setting changes the uppermost terminal position of the movable platen. This therefore requires that the press be set up all over again, such as by raising or lowering the position of the fixed platens, so that the fixture portions carried by re spective platens once again meet properly when the press is in its closed position.

It is an important feature of the present invention that changing the stroke setting does not affect the relation ship of the plates in the closed position of the press. Ac-

cordingly, once the setting is correctly established, it need not be altered merely because the stroke is changed.

When all of the crank pins have been positioned as shown in Figure 7, operation of the press may be commenced without further adjustment apart from speeding the rotation of gear 23 so as to take advantage of the shorter stroke. Operation of the press at the shorter stroke setting will cause each link 16 to assume the position shown in Figure 8 when the press is in its open position. It will be apparent that the press may be returned to long stroke operation by reversing the fore going operations.

Any suitable means may be provided for holding each crank pin in position while permitting its readyremoval when required. For example, as seen in Figure 5, each crank pin may have a transverse slot 38 for receiving a flat key 39. One of the ears of the crank arm is recessed at 40 to receive the key and the latter is held in position in the recess by means of a screw 41. With the screw holding the key in position, the crank pin will be locked against axial movement; however, the crank pin may easily be withdrawn from its position by first removing screw 41 so that key 39 may be shifted bodily with the pin.

In view of the foregoing it will be apparent to those skilled in the art that I have accomplished at least the principal object of my invention and it will also be apparent to those skilled in the art that the embodiment herein described may be variously changed and modified, without departing from the spirit of the invention, and that the invention is capable of uses and has advantages not herein specifically described, hence it will be appreciated that the herein disclosed embodiment is illustrative only, and that my invention is not limited thereto.

I claim:

1. A variable stroke press comprising a reciprocable platen having an extreme platen position, a crank pin olT-set radially of an axis and movable in an are thereabout, and link means extending between said crank pin and said platen for translating arcuate movement of the former to reciprocable movement of the latter, said crank pin being shiftable radially of said axis when said platen is in said extreme platen position to vary said oil-set relationship and thereby vary the distance through which said platen is reciprocated toward and away from said extreme platen position and said crank pin being simultaneously shiftable relative to said link means to provide for varying said off-set relationship while said platen remains fixed in said position.

2. A variable stroke press comprising a reciprocable platen having an extreme platen position, a crank arm mounted for movement about an axis toward and away from a predetermined position and having first and second apertures spaced from each other and also spaced different distances radially of said axis, a crank pin selectively receivable within either of said apertures and being movable with said crank arm in an are about said axis, and link means having first and second apertures each adapted to receive said crank pin and spaced apart a distance equal to the spacing between the apertures in said crank arm, said link means extending between said crank pin and said platen for translating arcuate move ment of the former to reciprocating movement of the latter and said link means apertures being aligned with respective apertures of said crank arm when the latter and said platen are disposed in their respective said positions, said crank pin being disposed in respective first apertures of said crank arm and said link means to provide for a given amount of reciprocation of said platen toward and away from said extreme platen position and said crank pin being shiftable from respective first apertures of said crank arm and said link means to respective second apertures thereof upon alignment of respective second apertures to vary the amount of reciprocation of said platen toward and away from said platen position Without afiecting such position.

3. A variable stroke press comprising a fixed platen and a movable platen and the latter having a terminal position adjacent the formed and being reciprocable toward and away from such position, a crank arm mounted for movement about an axis toward and away from a predetermined position and having first and second apertures spaced from each other and also spaced different distances radially of said axis, a crank pin selectively receivable within either of said apertures and being movable with said crank arm in an are about said axis, and link means having first and second apertures each adapted to receive said crank pin and spaced apart a distance equal to the spacing between the apertures in said crank arm, said link means extending between said crank pin and said movable platen for translating arcuate movement of the former to reciprocating movement of the latter and said link means apertures being aligned with respective apertures of said crank arm when the latter and said movable platen are disposed in their respective said positions, said crank pin being disposed in respective first apertures of said crank arm and said link means to provide for a given amount of reciprocation of said mov able platen toward and away from said terminal position and said crank pin being shiftable from respective first apertures of said crank arm and said link means to respective second apertures thereof upon alignment of respective second apertures to vary the amount of reciprocation of said movable platen toward and away from said terminal position without affecting such position.

4. Apparatus for reciprocating a movable member such as a press platen toward and away from a predetermined position, comprising a crank pin-oflF-set radially of an axis and movable in an arc thereabout, and link means extending between said crank pin and the member for translating arcuate movement of the former to reciprocatory movement of the latter toward and away from its predetermined position, said crank pin being selectively shiftable relative to said link means in a direction toward and away from said member and simultaneously shiftable relative to said axis in a direction toward and away therefrom to vary the distance through which said member is reciprocated toward and away from said predetermined position without affecting a change in the latter.

5. Apparatus for reciprocating a movable member such as a press platen toward and away from a predetermined position, comprising a crank arm rotatable about an axis and having spaced first and second apertures disposed different distances radially of such axis, a crank pin selectively receivable within either of said apertures and being movable in an arc with said crank arm about said axis, and link means having first and second apertures each adapted to receive said crank pin and spaced apart a distance equal to the spacing between said crank arm apertures, said link means extending between said crank pin and the movable member for translating arcuate movement of the former to reciprocatory movement of the latter, said crank pin being disposed in respective first apertures of said crank arm and said link means to provide for a given amount of reciprocation of said meniber toward and away from said predetermined position upon rotation of said crank arm and said crank pin being shiftable from respective first apertures of said crank pin and said link means to respective second apertures thereof to vary the amount of reciprocation of said member toward and away from said predetermined position upon rotation of said crank arm without affecting a change in such position.

References Cited in the file of this patent UNITED STATES PATENTS 1,918,784 Rode July 18, 1933 2,030,296 Horstmann Feb. 11, 1936 2,039,848 Shearman May 5, 1936 2,378,062 Byerlein June 12, 1945 2,747,509 Pool May 29, 1956 2,822,696 Staecker et a1. Feb. 11, 1958 

